While in the chair at the main menu press space bar a few times and you will get out of the chair.
Once out of the chair walk to the left and you will see a old computer walk up to it and press F and then you will have control of the terminal
Now type 3ARC INTEL to unlock all the intels for viewing and 3ARC UNLOCK to unlock all zombie maps and campaign missions.
Extras:
Type ZORK for a random game (Haven't tried it yet...)
Type DOA to play Dead Ops Arcade (Very fun!)
Enjoy!